1. Field of the Invention
The present invention relates generally to vertical lift rotary wing aircraft and, more particularly, to vertical lift aircraft having an enclosed rotary wing.
2. Brief Description of the Related Art
Vertical lift rotary wing aircraft are generally characterized by a main rotor blade forming a rotary wing for the aircraft and rotatable within a horizontal plane for forcing air downwardly to overcome the force of gravity and create vertical lift capable of rendering the aircraft airborne. Conventional rotary wing aircraft, such as helicopters, typically include a cabin or fuselage, a flexible main rotor blade mounted to the cabin, a tail rotor, vertical and horizontal stabilizers and landing gear. The cabin ordinarily contains an operator control area, a storage area and an engine compartment. The main rotor blade, which comprises the rotary wing for the aircraft, conventionally includes a plurality of main rotor blade members extending radially to a main rotor shaft. The main rotor blade members typically rotate about a central longitudinal axis of the main rotor shaft in a horizontal plane perpendicular to the central longitudinal axis of the main rotor shaft. The main rotor shaft is typically oriented with its central longitudinal axis perpendicular to the ground or other surface on which the landing gear is supported when the aircraft is not in flight. The controls for conventional vertical lift rotary wing aircraft normally comprise a vertical directional control system, a horizontal directional control system and a rotational directional control system. The vertical directional control system typically comprises a collective control stick, usually located at the left hand of the pilot or operator, connected to pitch controls located about the main rotor shaft to control vertical movements of the aircraft. Ordinarily the pitch controls mechanically connect the collective control stick to the main rotor blade to effect changes in the pitch of the main rotor blade symmetrically to vary or alter vertical lift. The horizontal directional control system typically comprises a cyclic control stick, normally located at the operator""s right hand, for controlling the horizontal direction of the aircraft. In many cases, horizontal directional control is effected via control rods connected to swash plates located on the main rotor shaft. The rotational directional control system typically comprises rudder foot pedals for operating the tail rotor to control yaw, i.e. rotation of the aircraft about its vertical axis, during slow flight or hovering.
Conventional rotary wing aircraft, primarily helicopters, exhibit noise, vibration, turbulence, a lack of safety and limited forward speed due to inadequacies in the main rotor blade control systems and the need to compensate for the differential effect of the wind on advancing and retreating main rotor blade members during forward flight. In conventional rotary wing aircraft such as helicopters, the horizontal directional control system usually requires a complicated system located about the main rotor shaft and which acts by reducing the pitch of each main rotor blade member on one side of the aircraft and increasing the pitch on the other side of the aircraft within a single rotational cycle, i.e. one complete rotation of the main rotor blade, to provide more lift in a desired direction. As a result, the potential for lift is negated or wasted on one side of the aircraft, causing a dynamic imbalance. The main rotor blade members thusly do not operate at maximum efficiency and power in that a significant amount of lift is lost from the total lift generated by the main rotor blade when effecting horizontal directional changes for the aircraft. In addition, vibration, turbulence and noise are created due to the main rotor blade members changing their pitch as they rotate. Since the main rotor blade in conventional rotary wing aircraft is not isolated from the relative wind, the main rotor blade exhibits flapping due to the differential speed between the advancing and retreating main rotor blade members caused by the relative wind meeting the advancing and retreating main rotor blade members during forward flight. Flapping of the main rotor blade inhibits lift and produces turbulence, vibration and noise. Also, the speed at the tips of advancing main rotor blade members must generally be reduced to a speed which, when combined with the speed of the relative wind, does not exceed the speed of sound. The need to reduce the advancing main rotor blade member tip speed decreases lift and further contributes to noise, vibration and turbulence. The turbulence, vibration and noise characteristic of conventional rotary wing aircraft contributes to pilot fatigue and stress, thereby limiting pilot endurance and increasing the chance for pilot error. The decreased centrifugal force resulting from a lowering of the main rotor blade tip speed increases coning (dihedral) of the main rotor blade plane and thusly impairs the stability of the main rotor blade plane with a concomitant reduction in lift. The requisite reduction in main rotor blade member tip speed requires that the overall speed of the aircraft also be reduced. Since each main rotor blade member does not have a constant pitch throughout all rotation angles, each main rotor blade member does not contribute its entire force to increasing lift during both hovering and forward movement.
Various types of vertical lift rotary wing aircraft have been proposed, as represented by U.S. Pat. No. 1,724,226 to Sorensen, U.S. Pat. No. 2,728,537 to Elkins, U.S. Pat. No. 2,777,649 to Williams, U.S. Pat. No. 3,750,980 to Edwards, U.S. Pat. No. 3,912,201 to Bradbury and U.S. Pat. No. 5,064,143 to Bucher. The Sorensen, Williams and Bucher patents disclose rotor blades at least partly enclosed in a housing, but are characterized by heavy and/or complicated structure as well as complex operational designs. Previously proposed vertical lift rotary wing aircraft having enclosed rotary wings utilize rigid main rotor blades that lack the ability to change pitch on the main rotor blades for rapid changes in vertical movements of the aircraft and/or lack the ability to perform an emergency auto-rotation with the aircraft. In order to be maximally effective, the control devices for the main rotor blades of previously proposed vertical lift rotary wing aircraft with enclosed rotary wings must be undesirably located close to the plane of the main rotor blades. Some prior vertical lift rotary wing aircraft with enclosed rotary wings employ a rigid, centrally reinforced and weighted ducted fan system with non-variable pitch main rotor blades, and some prior enclosed vertical lift rotary wing aircraft employ rotor blade systems having non-variable pitch rotor blades supported by rollers at the blade tips. Systems of the latter type are very heavy and also produce considerable resistance to the downdraft, resulting in decreased vertical lift. Many ducted fan systems disadvantageously require complex computer-controlled directional flaps.
In view of the above, there is a need for a vertical lift rotary wing aircraft with an enclosed rotary wing and which exhibits greater lift, forward speed and safety while reducing vibration, noise and turbulence. There is also a need for a vertical lift rotary wing aircraft with an enclosed rotary wing comprising a flexible main rotor blade of variable pitch to achieve rapid changes in vertical movements while horizontal directional control is accomplished without asymmetrical changes in pitch of the main rotor blade members which cause a dynamic imbalance. There is a further need for a vertical lift rotary wing aircraft with an enclosed rotary wing and permitting higher main rotor blade tip speed, permitting the pitch of each main rotor blade member to remain at the same setting through a single cycle, and reducing main rotor blade coning or dihedral.
Accordingly, it is a primary object of the present invention to overcome the aforementioned disadvantages of prior vertical lift rotary wing aircraft, such as conventional helicopters, as well as prior vertical lift rotary wing aircraft having an enclosed rotary wing.
Another object of the present invention is to increase lift and forward speed in a vertical lift rotary wing aircraft.
A further object of the present invention is to reduce vibration, noise and turbulence in a vertical lift rotary wing aircraft.
An additional object of the present invention is to increase safety in a vertical lift rotary wing aircraft by alleviating conditions that contribute to pilot stress and fatigue.
It is also an object of the present invention to increase safety in a vertical lift rotary wing aircraft having an enclosed rotary wing by permitting emergency auto-rotation of the aircraft to effect a safe landing.
Still another object of the present invention is to eliminate the need for asymmetrical pitch changes in the main rotor blade of a vertical lift rotary wing aircraft in order to achieve horizontal directional control.
Moreover, it is an object of the present invention to permit the main rotor blade tip speed to be increased to just below the speed of sound in a vertical lift rotary wing aircraft.
The present invention also has as an object to increase the stability of the main rotor blade plane in a vertical lift rotary wing aircraft.
Yet a further object of the present invention is to simplify horizontal directional control in a vertical lift rotary wing aircraft.
Additionally, it is an object of the present invention to isolate the main rotor blade of a vertical lift rotary wing aircraft from relative wind.
Some of the advantages of the present invention are that simple, relatively lightweight, variable pitch, flexible main rotor blades similar to those conventionally used in helicopters may be utilized in the vertical lift rotary wing aircraft; the flexible main rotor blade permits rapid changes in vertical movement of the aircraft to be effected; the use of a peripherally weighted, high momentum kinetic energy, rapidly responsive, variable pitch main rotor blade in a circumferential enclosure or housing permits execution by the vertical lift rotary wing aircraft of an emergency auto-rotation maneuver for safe landings in emergency situations; the vertical lift rotary wing aircraft is controlled in a manner similar to that of conventional helicopters so as to be familiar to pilots and avoid the need for extensive pilot training; the vertical lift rotary wing aircraft may include a rudder flap, elevator flaps and/or aileron flaps not normally found in conventional vertical lift rotary wing aircraft; horizontal directional control may be enhanced at sufficiently high forward speeds by the aileron, elevator and rudder flaps while the downdraft area remains open; the circumferential housing for the main rotor blade acts as an airfoil; at sufficiently high forward speeds, the housing contributes to stability of the aircraft, provides additional lift and allows virtually all of the main rotor blade power to be expended for forward speed; a horizontal orientation for the aircraft is permitted during forward flight while part of the aircraft""s power is dedicated to forward thrust; the control devices for horizontal directional control are advantageously located in the housing; the differential speed between advancing and retreating main rotor blade members is avoided; the tip speed of advancing main rotor blade members does not have to be reduced to a speed which, when combined with the speed of the relative wind does not exceed the speed of sound; the tip speed may be increased to just below the speed of sound, thereby increasing the stability of the main rotor blade plane, increasing lift and reducing noise, vibration, turbulence and operator fatigue; increased centrifugal force of the man rotor blade increases the stability of the main rotor blade plane and further increases lift; the overall speed of the vertical lift rotary wing aircraft can approach the speed of sound; the main rotor blade members have a constant pitch throughout all rotation angles so that each main rotor blade member contributes its entire force to increasing lift during both hovering and forward movements; each main rotor blade member operates at maximum efficiency and power; minimal lift is lost from the total lift of the aircraft when executing directional changes; the housing may be used to store emergency parachutes and flotation devices which are protected by the housing from contacting the rotating main rotor blade; safety is increased since the housing assists in preventing inadvertent contact with the rotating main rotor blade; the control devices are extendable radially outwardly and radially inwardly from the housing to achieve horizontal directional control in a radially inwardly extended position by obstructing a selected portion of the downdraft area while the control devices in a radially outwardly extended position increase stability of the aircraft and promote lift during forward flight; only a small portion of the downdraft area needs to be obstructed with the control devices to obtain horizontal directional control; banking in a desired direction may be facilitated via the use of the aileron flaps, which also provide drag to assist the rudder flap in controlling slipping and sliding during banking; the cabin may be located below or above the enclosed rotary wing; the housing may contain sealed air pockets which would enable the aircraft to float in water for emergency flotation; engine or motor power may be provided by a conventional reciprocating, turbo jet or jet engine; as an alternative to a tail rotor blade, a counter rotating rotor blade may be used in conjunction with the main rotor blade to control rotation of the aircraft about its vertical axis; and the tail rotor blade may also be shrouded for safety purposes for isolation from the main rotor blade wash and/or from the effects of the relative wind.
These and other objects, advantages and benefits are realized with the present invention as generally characterized in a vertical lift rotary wing aircraft comprising a cabin and a rotary wing mounted on the cabin to provide vertical lift for the aircraft. The cabin typically includes a cockpit or operator area containing a seat for a pilot or operator and a collective control, a rudder control and a cyclic control for use by the pilot to respectively control vertical, rotational and horizontal directional movements of the aircraft in flight. The rotary wing comprises an annular housing or enclosure and a main rotor blade rotatably disposed within the space circumscribed by an inner circumference of the housing. The main rotor blade is preferably a flexible main rotor blade of variable pitch whereby the pitch of the main rotor blade may be adjusted symmetrically via the collective control to control vertical directional movements of the aircraft. The space includes a downdraft area beneath the main rotor blade, and a horizontal directional control mechanism for the aircraft comprises a plurality of control slides spaced along the housing for retraction from and extension into the downdraft area. The control slides are slidably mounted in radial slots in the housing at 90 degree spaced locations and preferably there is a control slide at a forward location, a rearward location, a port location and a starboard location. The control slides have a neutral or retracted position in which the control slides are retracted radially outwardly from the downdraft area. The control slides are movable from the neutral position to an operational or extended position in which the control slides are extended radially inwardly into the downdraft area. In its operational position, each control slide preferably obstructs about four to five percent of the downdraft area. The control slides are preferably supported in the slots between upper and lower rollers, and an operating member is provided for each control slide by which the control slide is moved between the neutral and operational positions. The operating members may include a roller for each control slide, each roller being disposed in engagement with its corresponding control slide. The rollers are rotatable in a first direction to effect sliding movement of the control slides radially outwardly to the neutral position and are rotatable in a second direction to effect sliding movement of the control slides radially inwardly to the operational position. Each operating member preferably includes a servo mechanism operated via the cyclic control. When a selected one of the control slides is moved from the neutral position to the operational position while the aircraft is in flight, horizontal directional turning movement of the aircraft is effected in the direction of the control slide that has been moved to the operational position. When a pair of adjacent control slides are moved from the neutral position to the operational position while the aircraft is in flight, horizontal directional turning movement of the aircraft is effected in a direction between the pair of adjacent control slides that have been moved to the operational position. Horizontal directional control of the aircraft is accomplished via the control slides without asymmetrical pitch changes of the main rotor blade, thereby allowing the full effort of the main rotor blade to be used for lift and forward thrust. The housing isolates the main rotor blade from the relative wind such that flapping of the main rotor blade with its concomitant noise, vibration and turbulence is avoided.
Other objects and advantages of the present invention will become apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings, wherein like parts in each of the several figures are identified by the same reference characters.